Seepage is an important factor and serious disaster that affects the safe and long term services of submerged or partially submerged structures in irrigation works, maritime works, underground constructions and the like. Particularly, widespread damage and wreckage of earth and rockfill structures like earth and rockfill dams and embankments are caused by different levels of leakage and various problems derived by leakage. According to statistics, more than 90% of embankment breaching and more than one third of damages in earth and rockfill dam engineering in China are caused by seepage. Researching and developing advanced seepage positioning and orientating instruments, devices and distinguishing methods to reliably detect the position, range, direction and area of the seepage occurred in the submerged or partially submerged structures and take effective seepage prevention and resistance measures in time has extremely important significances for ensuring the engineering safety.
At present, submerged or partially submerged structures seepage positioning and orientating monitoring is mostly rested upon a point-type seepage sensor. However, missed monitoring often occurs since the monitoring points are limited. Moreover, most of the conventional seepage sensors have the defects of big volume, more leads, poor compatibility and the like. With the development of distribution type fiber sensing and monitoring technologies, works from engineering & science and technology industry pay increasing attention and involvement on researching and developing distribution type fiber identifying devices and methods that can be applied to seepage position and direction monitoring of submerged or partially submerged structures. However, most of the existing distribution type fiber seepage monitoring technologies at home and abroad are rested on a peripheral heat source to heat the fibers to be monitored; however, the safety of operating personnel will be threatened and the monitoring results will be affected if such situations as broken external package layer or electric leakage occurs. Moreover, it is difficult to guarantee a peripheral current heating system in the service environment of the submerged or partially submerged structures, which greatly hinders the application and popularization of the technology in actual engineering.